Compressed data scrambled distribution device and playback device thereof

ABSTRACT

The present invention provides a scrambled compressed data distribution device that can perform a high-resistance scrambled compressed data distribution by selectively using a plurality of types of scramble information and a playback device thereof. 
     A scrambling section scrambles compressed data by unique one of a plurality of scrambling methods. A hash value calculating section determines a hash value based on data b in a position where digital watermark data is not embedded, and an encrypting section encrypts the hash value with a secret key Sk(n) corresponding to the scrambling method and outputs an encrypted hash value c. A watermark data embedding section embeds the encrypted hash value in a watermark data embedding position of the data b and transmits the same as a compressed data stream d.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a compressed data scrambleddistribution device and a playback device controlled by a digitalwatermark thereof.

2. Description of the Related Art

Conventionally, methods for carrying out descrambling by use of digitalwatermark as key information have been proposed in the following PatentDocuments 1 and 2, for example.

Patent Document 1 discloses a method for generating a locking key by useof separately sent copyright information, player-specific information,and digital watermark information and carrying out descrambling basedthereon. In addition, Patent Document 2 discloses a method for applyingdescrambling to data when a trigger signal embedded in the form of adigital watermark exists and outputting without descrambling when thetrigger signal does not exist.

[Patent Document 1] Japanese Published Unexamined Patent Application No.2001-78007

[Patent Document 2] Japanese Published Unexamined Patent Application No.2002-534016

However, in both of the techniques, only one scramble signal is used,and there is no assumption that a plurality of types of scramble signalsare selectively used.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a scrambledcompressed data distribution device that can perform a high-resistancescrambled compressed data distribution by selectively using a pluralityof types of scramble signals and a playback device thereof. Also, it isanother object to provide a compressed data scrambled distributiondevice that can generate compressed data scrambled distribution signalsof a plurality of types of qualities and a playback device thereof.

In order to achieve the above-described object, the present inventionhas a first feature, in a compressed data scrambled distribution device,including a means for applying scrambling to compressed data by use ofany one of a plurality of scrambling methods, and a means for embeddinga signal to discriminate the used scrambling signal in the scrambledcompressed data as digital watermark data, and has a second feature inthat the digital watermark data is embedded after encryption.

Next, the present invention has a third feature, in a playback device,including a means for receiving compressed data distributed from thecompressed data scrambled distribution device, a means for extractingdigital watermark data from the received compressed data, and a meansfor determining a descrambling method based on the extracted digitalwatermark data and descrambling the received compressed data, and has afourth feature in that it includes a means for decrypting the digitalwatermark data.

Furthermore, the present invention has a fifth feature in that acompressed data scrambled distribution and playback device composed ofthe compressed data scrambled distribution device and playback device isprovided.

According to the present invention, since anyone of a plurality ofscrambling methods is selected and scrambling is thereby applied to onepiece of compressed data, a high-resistance compressed data scrambleddistribution signal can be generated.

Moreover, since it is sufficient for the playback device to include aplurality of descrambling methods notified in advance, no special deviceis required and data can be played back even by a portable telephone.

Moreover, since a plurality of scrambles can be applied in stages to onepiece of compressed data, when compressed data such as music data isdistributed via a portable telephone, a network, or the like, it becomeseasier to provide a user with the service and manage the same.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a schematic configuration of acompressed data scrambled distribution device according to an embodimentof the present invention.

FIG. 2 is a block diagram showing a schematic configuration of aplayback device according to an embodiment of the present invention.

FIG. 3 is an explanatory drawing of N types (ID(1) to ID (N)) ofscrambling methods and secret keys and public keys correspondingthereto.

FIG. 4 is an explanatory drawing when a plurality of scrambles isapplied in stages to one piece of compressed data.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, the present invention will be described in detail withreference to the drawings.

First, N types (ID(1) to ID(N)) of scrambling methods 1 to N as shown inFIG. 3 and secret keys and public keys corresponding thereto areprepared as a preliminary arrangement. Then, a compressed data scrambleddistribution device (server) can selectively use the N types ofscrambling methods to carry out scrambling. On the other hand, aplayback device (client) thereof has descrambling methods and publickeys based on the scrambling methods.

Next, a configuration and operations of a compressed data scrambleddistribution device according to an embodiment of the present inventionwill be described with reference to a block diagram of FIG. 1.

A compressed data preparing section 1 compresses input data a, forexample, music data, to prepare compressed data thereof. A scramblingsection 2 scrambles the compressed data by any scrambling method of theID(1) to ID(N). In the following, description will be given on theassumption that a scrambling method n corresponding to an ID(n) (here,1≦n≦N) has been selected. A digital watermark embedding position dataextracting section 3 extracts data in a position where digital watermarkdata is embedded. Data (non-embedding position data) b excluded data atthe position where digital watermark data is embedded by the digitalwatermark embedding position data extracting section 3 is sent to a hashvalue calculating section 4, and a hash value is determined based on thenon-embedding position data b. An encrypting section 5 encrypts the hashvalue with a secret key Sk(n) of the ID(n) and outputs an encrypted hashvalue c. A watermark data embedding section 6 embeds the encrypted hashvalue in a watermark data embedding position of the non-embeddingposition data b from the digital watermark embedding position dataextracting section 3 and transmits the same as a compressed data streamd.

Here, it is preferable that the data in a position where digitalwatermark data is embedded is data at a part that has little influenceon data quality and data to which scrambling is applied is data at apart that has influence on data quality.

Next, a configuration and operations of a playback device will bedescribed with reference to FIG. 2.

A compressed data receiving section 11 receives the compressed datastream d transmitted from the compressed data scrambled distributiondevice. A digital watermark extracting section 12 extracts digitalwatermark data from the compressed data. Non-embedding position data bbeing residual data after extracting the digital watermark data is sentto a hash value calculating section 13, where a hash value is calculatedbased on the data b. On the other hand, a hash value decrypting section14 decrypts an encrypted hash value extracted by the digital watermarkextracting section 12 by use of all public keys Pk(1) to Pk(N) describedabove. Then, a comparing section 15 compares the hash values decryptedby use of the public keys Pk(1) to Pk(N) with the hash value determinedby the hash value calculating section 13. If there is any coincidenthash value as a result of this comparison, the compressed data receivedby the compressed data receiving section 11 is descrambled with adescrambling section 16 by a descrambling method corresponding to apublic key Pk(n) used for encryption of that hash value. With regard todecryption of the hash value, at a stage where the decrypted hash valuehas coincided with the hash value determined by the hash valuecalculating section 13, decryption by use of other remaining pubic keysmay be stopped.

The descrambled compressed data is sent to an unillustrated compresseddata playback device and reproduced. On the other hand, when the data isaltered in the middle of transmission or the like, it is judged in thecomparing section 15 that no hash value coincident with the hash valuedetermined by the hash value calculating section 13 is included in thehash values decrypted by use of the public keys Pk(1) to Pk(N), and thedata is sent to the compressed data playback device without beingdescrambled or output of the data is abandoned.

As in the above, according to the present embodiment, since thecompressed data scrambled distribution device can scramble compresseddata by use of any method of the plurality of scrambling methods 1 to N,it becomes possible to generate a high-resistance compressed datascrambled distribution signal.

Next, by making the respective scramble strength of the plurality ofscrambling methods 1 to N variable, for example, so that scramblegradually strengthens, when, for example, music data is provided for auser via a portable telephone, a network, or the like, a clear sound ofmusic without scramble is first provided to allow the user listen to themusic to find out whether he/she likes the music. Then, if the userwishes to listen to the music further, it is possible to worsen themusic quality in stages for a user who has no playback functionaccording to the present invention. On the other hand, a user who hasthe playback function according to the present invention can listen to aclear piece of music until the end.

Also, as another method, scramble strength is made to strengthengradually from scramble 1 to scramble N, and for example, as shown inFIG. 4, operations such as providing a data part to which no scramblingis applied at an introduction part C(0) of compressed data such as musicdata, applying a weak scramble 1 to the following part C(1), applying aslightly strong scramble 2 to the following part C(2), and furthermore,applying the strongest scramble 3 to the following part C(3) can becarried out. This makes it possible, when, for example, music data isprovided for a user via a portable telephone, a network, or the like, toprovide a clear sound of music without scramble at the introduction partC(0) thereof and worsen the music quality in stages for the user who hasno playback function according to the present invention as it progressesto the parts C(1), C(2), and C(3).

In the above-described embodiment, the N types (ID(1) to ID(N)) ofscrambling methods shown in FIG. 3 and the secret keys and public keyscorresponding thereto have been fixed, however, the present invention isnot limited thereto and these can be made variable. These can be changedin a cycle such as daily or weekly, for example. This change must benotified in advance to the playback device.

The present invention is not limited to music data and can also beapplied to video data or the like. For a higher secrecy, a public keycertificate can be used and attached to data for transmission.

The inventor has already confirmed that when MPEG-1/2 Layer III (MP3)defined by ISO is used as compressed data, it is possible, in a portableterminal, to determine a predetermined descrambling method of aplurality of types of scrambles based on an embedded signal anddescramble the compressed data in real time.

1. A distribution and playback device comprising: the distributiondevice including: a predetermined plurality of different scramblingmethods; means for scrambling compressed data to produce scrambledcompressed data by use of a selected one of the plurality of scramblingmethods; means for extracting data (D) in a position where digitalwatermark is embedded from the scrambled compressed data; means forcalculating a hash value based on a non-embedding position scrambledcompressed data which do not include the data (D); means for encryptingthe hash value with a secret key assigned to the selected one of theplurality of scrambling methods; and means for embedding the encryptedhash value at a watermark data embedding position in the scrambledcompressed data; the playback device including: means for receiving thescrambled compressed data from the distribution device; means forextracting the digital watermark from the received scrambled compresseddata; means for calculating a hash value based on a non-embeddingposition received scrambled compressed data which do not included thedigital watermark; means for decrypting the encrypted hash value by useof all public keys assigned to the plurality of scrambling methods;means for determining a descrambling method by a coincident of thecalculated hash value with the decrypted hash value; and means fordescrambling the received scrambled compressed data with thedescrambling method.
 2. The distribution and playback device accordingto claim 1, wherein a strength of scrambling methods is changed step bystep.